(cba:news) TT Ari in its darkest lair

[Joe Patterson]

Dear CBAers,

Some amazing light curves of the quiescent TT Ari coming from the 
western USA observers, plus Mike Potter in Maryland who has managed to 
extend the coverage by 2-3 hours to the east.   I'm still hoping for 
good things from Europe, but I fear that weather there has turned bad - 
except for Enrique Agustino (Spain) who has been waging a heroic 
struggle with a 4-inch telescope (I think!).  Just a little, so far, 
from NZ and AU, but hope springs eternal there too.

I've never seen anything like these light curves.  In fact, no one has - 
not for TT Ari, and not for any other CV.  About 7 out of every 11 
hours, the star is down at V=16.3, and shows the ORBITAL period - for 
the first time ever.  There is then no activity, just a "heating" light 
curve which is likely the result of the hot WD illuminating the 
secondary's face.  Then the star goes into convulsions at V~15 for 4 
hours, then rests again... to repeat the cycle about every 11 hours. 
Just flat astounding.

So far, we've learned more from the V (or, if you can't spare the 
photons, clear) light curves than from the multicolor photometry.  But 
that's probably because it has been at true quiescence for only 1 week. 
  Fortuitously I'm about to leave on an observing run with the 2.4 m 
telescope; if weather permits, I'll spin filters and likely deconvolve 
this star into M dwarf and hot WD.  The flickering itself, when it's 
there, is broadband and not too likely to cough up much information from 
multiband observations.  I slightly recommend choosing one filter and 
sticking with it.  Also, there's value in preserving your setup as much 
as feasible; I've had enough simultaneous coverage to calibrate the 
various observers.

I say "slightly recommend" because this is in the absence of real 
knowledge about what we are observing.  A year from now, I'll have a 
more definite opinion about how we *should* have observed it!

More info about other stars tomorrow.  Is there help on the way from 
other longitudes re TT Ari?  It would be great - the coherence of this 
11 hour cycle is far from established, and it's a damn tough periodicity 
to evaluate!

joe